Experimental Study of Hydrogen Generation During Low Temperature Basalt-Water Interaction

Hydrogen generated from the reaction of water with basalt has been proposed as a source of metabolic energy to support subsurface autotrophic microbial communities in both terrestrial and seafloor settings. However, few experimental studies have examined the production of hydrogen from basalt-water interactions at low temperature (e.g., Stevens and McKinley, Science, 1995; ES & T, 2000), and the reactions that might be responsible for hydrogen production remain poorly known. In order to address this issue, we have initiated an experimental study to examine hydrogen production in basaltic systems. Initial experiments have been conducted by reacting basalt powder with water in glass vials, and monitoring hydrogen in the headspace. The experiments encompass a range of temperature (25-100 ° C), pH (5-9) and grain size. Results indicate that within the first few days hydrogen is produced rapidly, in agreement with previous studies. However, the production rates taper off rapidly with continued reaction, indicating that initial rates are not indicative of long-term hydrogen generation in natural systems. Significantly, although previous studies (Stevens and McKinley, 1996, 2000) had concluded that reaction of the mineral olivine is the primary source of hydrogen production in basalt, we find this mineral to be unreactive at temperatures of 100 ° C and lower.